1. Field of the Invention
This invention relates to a method for producing gallium nitride powders and an apparatus for producing the gallium nitride powders which are preferably employed as fluorescent powders to make an optical display.
2. Description of the Prior Art
Recently, a short wavelength semiconductor laser and a light-emitting diode which utilize excellent light emission performance of GaN-based III nitride semiconductor come into practical use, and also, an optical display which utilizes fluorescent properties of GaN is developed.
In the application of GaN for the optical display, it is required to prepare GaN powders, which can be made by following the technique, for example, disclosed in Japanese Patent Application Laid-open 2000-198978 where ammonia solution is dropped in gallium nitric hydrate solution to form gallium hydroxide, and then, obtain porous gallium oxide through moisture elimination, which is heated under ammonia atmosphere to obtain the GaN powders.
Moreover, the GaN powders can be made by means of the technique disclosed in J. American Ceramic Society, 79, 2309-2312 (1996) where metallic gallium is heated within a temperature range of 900-1000° C. and melted to form gallium melt, which is chemically reacted with ammonia gas to obtain the GaN powders.
In a conventional producing method of GaN powders as mentioned above, however, it takes long time of several hours to several days in batch process, so the production efficiency is extremely low and the mass production can not be realized. As of now, therefore, a practically usable producing method and apparatus of GaN powders can not be provided.